Adipose Tissue Gene Expression of Entire Male, Immunocastrated and Surgically Castrated Pigs.

Klavdija Poklukar,Kevin Kress,Milka Vrecl,Martin Škrlep,Marjeta Čandek-Potokar,Nina Batorek-Lukač,Volker Stefanski,Gregor Fazarinc

doi:10.3390/ijms22041768

Abstract

Differences in adipose tissue deposition and properties between pig male sex categories, i.e., entire males (EM), immunocastrates (IC) and surgical castrates (SC) are relatively well-characterized, whereas the underlying molecular mechanisms are still not fully understood. To gain knowledge about the genetic regulation of the differences in adipose tissue deposition, two different approaches were used: RNA-sequencing and candidate gene expression by quantitative PCR. A total of 83 differentially expressed genes were identified between EM and IC, 15 between IC and SC and 48 between EM and SC by RNA-sequencing of the subcutaneous adipose tissue. Comparing EM with IC or SC, upregulated genes related to extracellular matrix dynamics and adipogenesis, and downregulated genes involved in the control of lipid and carbohydrate metabolism were detected. Differential gene expression generally indicated high similarity between IC and SC as opposed to EM, except for several heat shock protein genes that were upregulated in EM and IC compared with SC. The candidate gene expression approach showed that genes involved in lipogenesis were downregulated in EM compared with IC pigs, further confirming RNA-sequencing results.

Highlights

Castration of male piglets has been practised for centuries, mainly to prevent consumers’ negative response to boar taint
Before the second vaccination (V2), IC pigs are metabolically equal to entire males (EM) [11,12], but after V2, their metabolism progressively turns towards more castrate-like, with a notable increase in feed intake and fat tissue deposition [13,14], which increases almost linearly with the time elapsed from the V2 to slaughter [15]
The objective of our study was to characterize the underlying molecular processes occurring in the adipose tissue of EM, IC and surgical castrates (SC) pigs using two approaches: the detection of differentially expressed genes and identification of gene networks using RNA-seq on pooled RNA; validation of differentially expressed genes discovered by RNA-seq as well as measuring the expression of pre-selected candidate genes involved in lipid metabolism on individual animals by quantitative PCR (qPCR)

Summary

Introduction

Castration of male piglets has been practised for centuries, mainly to prevent consumers’ negative response to boar taint. The second alternative is immunocastration, which is a procedure of immunogenic blocking of testicular function consisting of the vaccination against endogenous gonadotropinreleasing hormone (GnRH) causing a castration-like effect [10,11]. According to the most common vaccination practice, the first dose is administered early in life at around 10–12 weeks of age, and the second dose is administrated at around 19–21 weeks (i.e., 4–6 weeks before slaughter), which denotes that the deprivation of male hormones is effective later than in the case of SC. Before the second vaccination (V2), IC pigs are metabolically equal to EM [11,12], but after V2, their metabolism progressively turns towards more castrate-like, with a notable increase in feed intake and fat tissue deposition [13,14], which increases almost linearly with the time elapsed from the V2 to slaughter [15]. We recently demonstrated [16] that the increase in quantity of fat depots after immunocastration is associated with a larger adipocyte and lobulus surface area in the backfat, together with notably increased activity of lipogenic enzymes (i.e., fatty acid synthase, glucose 6-phosphate dehydrogenase, malic enzyme and citrate cleavage enzyme) and increased fat saturation as a result of the elevated de novo synthesis of palmitic and stearic acids

Objectives

Methods

Results

Discussion

Conclusion